WASHINGTON — As the recent flap involving Republican presidential hopeful Rick Santorum shows, the mix of politics and religion is not a marriage made in heaven.

Indeed, Thomas Jefferson said long ago that a "wall" needed to be built to separate church and state. John F. Kennedy reaffirmed it and the courts have long upheld it.

But in the heat of a tight, nail-clawing Republican contest for the presidential nomination, a more than 200-year-old constitutional value has become campaign fodder.

As 10 states prepare to hold Super Tuesday presidential primaries next week, it's also become just one act in a larger, but familiar, political drama.

Even as poll after poll shows that jobs and the economy are the public's primary concerns, long-divisive social issues involving matters of personal faith and beliefs this week became an increasing part of the effort to win the White House, as well as dominance on Capitol Hill.

While Santorum has tried to keep the issue at bay, with the political stakes so high, the debate probably will continue.

"The impact of religion on politics never really goes away," said John Green, a political science professor at the University of Akron and senior fellow at the Pew Forum on Religion & Public Life. "Several of the candidates have determined, rightly or wrongly, that these issues are the way they can distinguish themselves.

"It's part of a broader pattern in American presidential politics that in order to win a primary, candidates frequently may have to run toward the party's base."

That's where Santorum was heading last weekend when he said that, upon reading Kennedy's 1960 speech in which the late president said the church-state divide was absolute, he "almost threw up."

A week earlier, the former senator from Pennsylvania told an audience in Ohio that President Barack Obama, who's explained his Christian faith on several occasions, practiced "some phony theology ... not a theology based on the Bible."

Mitt Romney and Newt Gingrich, two of Santorum's Republican competitors, also have accused the president of waging a war on religion. It's the kind of rhetoric that triggers applause in some quarters of the GOP's primary electorate.

"I do like his values," Dan Lasecki, a Michigan retiree, said of Santorum, who narrowly lost his state's primary this week to Romney, a former governor of Massachusetts. "The country is being degraded to the point where too many people don't have those values."

But on matters of personal faith and politics, not everyone in the GOP is sitting in the same pew, or even inside the church. Many worry that a Republican revival of the so-called "culture wars" of the 1980s is a troublesome path to political salvation this year.

This week, Republican senators tried to allow employers and insurance companies to withhold coverage for contraceptives and other services if they have religious or moral objections to them.

In Virginia, Republican lawmakers want women to be forced to undergo abdominal ultrasounds — initially they required a type of ultrasound that uses a vaginal probe — before abortions. Elsewhere, they're backing "personhood" initiatives to amend state constitutions to say that "person" applies to everyone from the moment of conception.

"The cultural and social issues have always been of great importance to the core of the Republican Party," Republican Sen. Lamar Alexander of Tennessee, who twice ran for his party's presidential nod, said in an interview. "But our nominee had better address how he is going to make it easier to create higher incomes and more jobs in the United States. If there's not a Republican answer to that, we'll get President Obama."

Invoking religion is often a political dog whistle to pivotal parts of the electorate, according to Carol Swain, a professor of law and politics at Vanderbilt University Law School in Tennessee, a Super Tuesday state.

"It's very important in a state like Tennessee," said Swain, a self-described Christian conservative. "That's the heart of the Bible Belt. People who are religiously devout feel that they are under attack, and that's driving more people to elevate a candidate's religious stance in their decisions."

Whether that crosses some constitutional line is all in the eye of the beholder.

Liberals often decry the mix of religion and politics. But where would the great progressive causes of the 1960s, such as the civil rights movement and the Vietnam War protests, have been without the church?

Conservatives often champion it, except when they don't. After the president spoke at last month's National Prayer Breakfast about his faith and how it informed his views on public policy, including shared sacrifice and taxes, Republican Sen. Orrin Hatch of Utah offered a withering retort: "I think most Americans would agree that the Gospels are concerned with weightier matters than effective tax rates."

Jefferson and the other Founding Fathers included freedom of religion when they wrote the First Amendment because they wanted to choke off any attempt to establish a national religion. That was one of the reasons that the colonists left England for America in the first place.

"Thus building a wall of separation between church and state," Jefferson later wrote.

But curtailing expressions of faith in the public square — at a political town hall meeting, for instance — is different from the courts ordering the removal of crosses or Stars of David from the grounds of a public building.

Several scholars said it would be impossible to separate faith from the beliefs, political and otherwise, that people bring to public debate.

But when "vague" terms such as "separation of church and state" get tossed around, people end up "talking past each other," said Eugene Volokh, a professor of constitutional law at the University of California, Los Angeles.

Santorum said Kennedy's speech nauseated him because "the idea that the church can have no influence or no involvement in the operation of the state is absolutely antithetical to the objectives and vision of our country."

Kennedy biographer Robert Dallek said Santorum either missed Kennedy's point or was "political posturing" to win favor with evangelical voters.

In September 1960, Kennedy was a Democratic senator from Massachusetts who was running for president at a time when no Roman Catholic had ever reached the White House. In his speech to a convention of Protestant ministers in Houston, Kennedy wanted to dispel the suspicion that, should he win, he would be taking orders from the pope.

Kennedy "honored the tradition of separation of church and state," Dallek said. "It was as simple as all that."

Noting that Santorum is also Catholic, Dallek said, "What Santorum should understand is, if it were not for John Kennedy being elected, he wouldn't have a ghost of a chance today."